Nothing else in life will make you feel more stupid than a really tricky riddle.
This is one of those.
While some (mainly those who enjoy Sudoku and the cryptic crossword) may argue riddles are fun, others (the rest of the world) would suggest they're stressful and rage-inducing.
Despite a beautifully put together animation courtesy of Ted-Ed, this brain muddle about four people, a bridge and some zombies will really, really force you to question your IQ.
Try it for yourself, if you can stomach the 100% guaranteed irritation.
Please, do let us know how long it took you (if you even managed to) solve this riddle. We're still working on it.